MongoDB: Search minimum, maximum in nested object with dynamic field name - mongodb

Question

I have a query to get the minimum query and maximum query on below sample data set. In my case fields names are dynamic, like below product_1, product_2...
{
"_id" : NumberLong(540),
"product_1" : {
"orderCancelled" : 0,
"orderDelivered" : 6
},
"product_2" : {
"orderCancelled" : 3,
"orderDelivered" : 16
},
"product_3" : {
"orderCancelled" : 5,
"orderDelivered" : 11
}
}
I am not getting an idea how can i do this in Mongo where the field names are dynamic, means in future there may be other products also get created as product_4 and product_5 for the same id.
I need a query which gives me minimum value for orderDelivered and maximum value for orderCancelled, as for example in above document result will be orderDelivered:16 & orderCancelled:0 .
Thanks for any idea.

Answer 1

You should restructure your document so that all product documents are in an array:
{
"_id": NumberLong(540),
products: [
{
"name": "product_1",
"orderCancelled": 0,
"orderDelivered": 6
},
{
"name": "product_2",
"orderCancelled": 3,
"orderDelivered": 16
},
{
"name": "product_3",
"orderCancelled": 5,
"orderDelivered": 11
}
]
}
Then you'll be able to issue normal max/min queries like this:
db.test.aggregate([
{
$match: { "_id" : NumberLong(540) }
},
{
$unwind: "$products"
},
{
$group: {
_id: "$_id",
minDelivered: { $min: "$products.orderDelivered" },
maxCancelled: { $max: "$products.orderCancelled" }
}
}
])

Answer 2

You need to change your documents structure by updating them. You will need loop through each document using the .forEach method then $unset all field's name that startswith product_. From there you will need to add new fields products which is array of products using the $set update operator. That being said you should use "bulk" operations to update your documents for maximum efficiency
var bulkOp = db.collection.initializeOrderedBulkOp();
var count = 0;
db.collection.find().forEach(function(doc) {
var allproducts = [];
for(var key in doc) {
if(Object.prototype.hasOwnProperty.call(doc, key) && /^product_\d+/.test(key)) {
var product = {};
product["name"] = key;
product["orderCancelled"] = doc[key]["orderCancelled"];
product["orderDelivered"] = doc[key]["orderDelivered"];
allproducts.push(product);
var unsetField = {};
unsetField[key] = "";
bulkOp.find({"_id": doc._id}).update({ "$unset": unsetField });
};
count++;
};
bulkOp.find({"_id": doc._id}).update({
"$set": { "products": allproducts }
});
count++;
if(count % 500 === 0) {
// Execute per 500 operations and re-init
bulkOp.execute();
bulkOp = db.collection.initializeOrderedBulkOp();
}
})
// clean up queues
if(count > 0) {
bulkOp.execute();
}
Your documents will now look like this:
{
"_id" : NumberLong(542),
"products" : [
{
"name" : "product_1",
"orderCancelled" : 0,
"orderDelivered" : 6
},
{
"name" : "product_2",
"orderCancelled" : 3,
"orderDelivered" : 16
},
{
"name" : "product_3",
"orderCancelled" : 5,
"orderDelivered" : 11
}
]
}
Then comes your aggregation query using the .aggregate() method:
db.collection.aggregate([
{ "$match": { "_id": 542 } },
{ "$unwind": "$products" },
{ "$group": {
"_id": "$_id",
"maxOrderCancelled": { "$max": "$products.orderCancelled"},
"minOrderDelivvered": { "$min": "$products.orderDelivered"}
}}
])
Which returns:
{ "_id" : NumberLong(542), "maxOrderCancelled" : 5, "minOrderDelivvered" : 6 }
From version 3.2 you can use the $max and $min in your $project stage which is a much more better way to do this because there no need to $unwind your array first.
db.collection.aggregate([
{ "$match": { "_id": 542 } },
{ "$project": {
"maxOrderCancelled": {
"$max": {
"$map": {
"input": "$products",
"as": "order",
"in": "$$orc.orderCancelled"
}
}
},
"minOrderDelivered": {
"$min": {
"$map": {
"input": "$products",
"as": "orc",
"in": "$$orc.orderDelivered"
}
}
}
}}
])
Which yields:
{ "_id" : NumberLong(542), "maxOrderCancelled" : 5, "minOrderDelivered" : 6 }